The present invention relates to a pump wheel and/or turbine for a hydrodynamic transformer. The turbine and/or pump wheel each comprises an outer shell, an inner ring and a plurality of blades. Such transformers, also known as Fottinger speed transformers (Dubbel: "Taschenbuch fuur Maschinenbau" [Handbook of Mechanical Engineering], vol. 14, pp. 904 et seq.), are preferably used for the transfer of hydrodynamic output, that is, the transfer of a torque from a driving pump wheel to a turbine wheel using a circulating, output-transferring fluid (typically oil).
The known turbine and pump wheels (hereinafter referred to as turbine wheels) typically comprise deep-drawn and bent sheet metal elements having a shell and blade structure. Turbine wheels comprised of sheet metal typically require an elaborate construction of individual sheet metal pieces connected together, by inserting a sheet metal tongue of one piece into a corresponding recess in another sheet metal piece, and subsequently bending the tongue over. However, these connections disturb the evenness of the inner and outer surfaces of the turbine wheel in an area of the flowing fluid. Further, the fluid can leak at the penetration point of the sheet metal tongue into the corresponding recess, thus resulting in flow losses and reduced efficiency. Alternatively, the individual sheet metal elements may be welded together.
Turbine wheels comprised of plastic are also known, wherein a hollow chamber of the turbine wheel is formed using a core which is subsequently melted out. Alternatively, the individually produced plastic elements are bonded by ultrasound. Turbine wheels made of plastic are considerably lighter than turbine wheels made of metal. Therefore, plastic turbine wheels have a reduced moment of inertia.